1. FIELD OF THE INVENTION
The present invention relates to a process for producing a crystalline aromatic polyester.
2. DESCRIPTION OF THE PRIOR ART
In recent years crystalline aromatic polyesters are used for various industrial materials since these polyesters are superior in heat resistance and solvent resistance. The slurry polycondensation and the bulk polycondensation processes are known as the processes for producing aromatic polyesters.
However, such a slurry polycondensation process has problems in that the crystalline aromatic polyester produced thereby exhibits variations in physical properties because its particle size distribution is not enough uniform, and that the product polyester tends to develop color because of its insufficient heat stability. Another problem of this process is that high reaction temperatures, as compared with low reaction temperatures, raises the molecular weight of product but causes the used solvent to remain in the product, which therefore needs to be washed to remove the remaining solvent. Whereas, a bulk polymerization process without using any solvents is reasonable because it can simplify or omit a post-treatment process, for example, a washing or produced polymer. However, the bulk polycondensation process has many problems which are an un-uniformity of polymer melt with high viscosity and an adhesiveness of polymer to walls of reaction vessel.